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PubMed This is a summary of 23 peer-reviewed journal articles Updated
Emergency Medicine

Symptoms and Emergency Warning Signs

At a Glance

With complement factor H deficiency, fever or acute illness during eculizumab or ravulizumab treatment needs urgent medical advice because meningococcal disease can progress rapidly. Sudden loss of urine, confusion, seizures, chest symptoms, severe abdominal pain, or vision loss require emergency care.

Managing a condition related to Complement Factor H (CFH) means becoming an expert in your own body’s signals. Because this condition can affect your kidneys, blood, and eyes, you need to know which symptoms are a “check-in with the doctor” and which are a “go to the emergency room immediately” [1][2].

The Lifesaving Red Flag: Meningococcal Risk

If you are treated with medications like eculizumab or ravulizumab (C5 inhibitors), you are at a significantly higher risk for meningococcal disease, a life-threatening infection of the blood or the lining of the brain, as well as other serious Neisseria infections [3][4]. This risk exists even if you have been vaccinated [5].

Seek emergency medical advice or care immediately if you experience any of the following:

  • Fever and chills: A sudden high temperature [6].
  • Headache and neck stiffness: A severe headache often accompanied by a stiff neck that makes it hard to touch your chin to your chest [7].
  • Confusion or sleepiness: Feeling unusually drowsy, confused, or having trouble staying awake [8].
  • A dark purple or red rash: Small spots or large bruises that don’t fade when pressed [1].
  • Nausea and vomiting: These can be early signs of infection in patients on C5 inhibitors [6].
  • Sensitivity to light: Bright lights causing pain in the eyes [7].

Any fever or acute illness while receiving a C5 inhibitor requires immediate medical advice. Do not let emergency providers delay emergency antibiotics while waiting to obtain your medical records.

Emergency Signs of a TMA Crisis

In Atypical Hemolytic Uremic Syndrome (aHUS), the immune system can cause a “crisis” called Thrombotic Microangiopathy (TMA), where tiny blood clots form throughout the body [1][9].

Go to the Emergency Room if you notice these “crisis” signs:

  • Absence of Urine: A sudden marked reduction or absence of urine should prompt urgent assessment immediately [10].
  • Neurological Changes: Sudden confusion, seizures, fainting, or weakness in your arms or legs [11][12].
  • Chest Pain or Shortness of Breath: These may indicate the heart or lungs are being affected [13][14].
  • Severe High Blood Pressure: A sudden, extreme spike in your blood pressure readings [13].
  • Severe Abdominal Pain: Intense stomach pain, sometimes with bloody diarrhea [15][16].

Symptoms Requiring Same-Day Clinical Advice

Some symptoms are not immediately life-threatening but mean your condition is becoming active and needs same-day clinical advice or evaluation. Contact your specialist team immediately if you notice:

Kidney and Blood Changes

  • Changes in Urine: Urine that looks newly dark like tea or cola (blood), or urine that is markedly foamy (protein) [17][18].
  • New Swelling (Edema): Puffiness in your face (especially around the eyes) or swelling in your ankles and feet [19].
  • Unusual Bruising or Bleeding: Tiny red or purple dots on the skin (petechiae) or easy bruising [1].
  • Extreme Fatigue and Pallor: Feeling severe exhaustion and looking much paler than usual, which may signal anemia (low red blood cells) [1][20].
  • Jaundice: A new yellow tint to the whites of your eyes or your skin [1].

Vision Changes

Because CFH deficiency affects the back of the eye (the retina), you should report any of the following for an emergency or same-day eye assessment:

  • Sudden Vision Loss: A rapid loss of central or peripheral vision.
  • A “Curtain” or Shadow: A dark shadow falling over part of your vision.
  • Flashes or Floaters: Sudden bursts of light or floating spots [21].
  • Distorted Vision (Metamorphopsia): Straight lines (like door frames) appearing wavy or crooked (an Amsler grid can track this central vision change, but is not reliable for peripheral vision) [22].

Emergency vs. Same-Day Care Summary

Feature Emergency Room (Now) Same-Day Clinical Advice
Mental State Seizures, confusion, fainting Severe worsening fatigue
Infection High fever, stiff neck, rash Mild cold symptoms, no fever
Breathing Severe shortness of breath Mildly out of breath with activity
Urination Sudden marked reduction or absence New foamy, dark, or tea-colored urine
Physical Signs Chest pain, severe abdominal pain New edema, jaundice, or petechiae
Vision Sudden loss, flashes, or a curtain Gradual changes or mild waviness

When in doubt, always call your specialist’s “on-call” line. It is better to report a symptom that turns out to be minor than to ignore a sign of your immune system’s “brakes” failing [23].

Common questions in this guide

Which symptoms mean I should go to the emergency room with CFH deficiency?
Go to the emergency room for a sudden major drop or absence of urine, seizures, confusion, fainting, new weakness, chest pain, severe shortness of breath, very high blood pressure, severe abdominal pain, or sudden vision loss. These can signal a thrombotic microangiopathy crisis or serious organ involvement and should not wait for a routine appointment.
Why does a fever need urgent attention during eculizumab or ravulizumab treatment?
These C5-inhibitor medicines greatly increase the risk of meningococcal disease and other serious Neisseria infections, even if you have been vaccinated. Any fever, chills, or acute illness requires immediate medical advice; tell emergency staff about the medicine and do not let obtaining records delay urgent antibiotics.
What urine changes should I report if I have complement factor H deficiency?
New tea- or cola-colored urine, blood in the urine, or markedly foamy urine can indicate kidney involvement and needs same-day advice from your specialist team. A sudden marked decrease or absence of urine is an emergency and requires immediate assessment.
Which changes in vision need urgent assessment?
Sudden vision loss, a curtain or shadow, or new flashes and floaters should be treated as urgent warning signs and may require emergency or same-day eye assessment. Wavy or distorted straight lines also need prompt clinical advice; an Amsler grid can help track central vision but cannot reliably check peripheral vision.
What is a TMA crisis in aHUS?
A thrombotic microangiopathy crisis is a serious episode in which tiny blood clots form throughout the body and can injure organs. Confusion, seizures, fainting, weakness, reduced urine, chest symptoms, severe high blood pressure, or severe abdominal pain require emergency care.
What should be in my CFH deficiency emergency plan?
Ask your specialist team for a written plan that names the hospital to use, explains your risk of TMA and meningococcal disease, and lists your current medicines. Keep your eculizumab or ravulizumab safety card available and know your usual platelet count, creatinine, and urine protein results so changes can be recognized quickly.

Get notified when new evidence is published on complement factor H deficiency.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.

References

References (23)
  1. 1

    [Ultra-early administration of eculizumab in a child with atypical hemolytic uremic syndrome: a case report].

    Guo DD, Xiao YX, Wang WR, et al.

    Zhongguo dang dai er ke za zhi = Chinese journal of contemporary pediatrics 2025; (27(11)):1408-1413 doi:10.7499/j.issn.1008-8830.2503084.

    PMID: 41250542
  2. 2

    A Narrative Review of C3 Glomerulopathy: From Pathogenesis to Targeted Therapy.

    Jauhal A, Barr B, Girard L, et al.

    Canadian journal of kidney health and disease 2026; (13()):20543581261442656 doi:10.1177/20543581261442656.

    PMID: 42131278
  3. 3

    High Risk for Invasive Meningococcal Disease Among Patients Receiving Eculizumab (Soliris) Despite Receipt of Meningococcal Vaccine.

    McNamara LA, Topaz N, Wang X, et al.

    MMWR. Morbidity and mortality weekly report 2017; (66(27)):734-737 doi:10.15585/mmwr.mm6627e1.

    PMID: 28704351
  4. 4

    An evaluation of ravulizumab for the treatment of neuromyelitis optica spectrum disorder.

    Balaban DT, Levy M, Borrow R, Anderson MR

    Expert opinion on biological therapy 2024; (24(11)):1193-1198 doi:10.1080/14712598.2024.2423002.

    PMID: 39460545
  5. 5

    Case report: Benefits and challenges of long-term eculizumab in atypical hemolytic uremic syndrome.

    Cullinan N, Gorman KM, Riordan M, et al.

    Pediatrics 2015; (135(6)):e1506-9 doi:10.1542/peds.2014-3503.

    PMID: 25941307
  6. 6

    High risk and low incidence diseases: Meningococcal disease.

    Cejin MC, Koyfman A, Long B

    The American journal of emergency medicine 2026; (99()):114-122 doi:10.1016/j.ajem.2025.09.031.

    PMID: 41016083
  7. 7

    Breakthrough serogroup Y meningococcal disease in a vaccinated patient with myasthenia gravis receiving ravulizumab: a case report.

    Strugar SŠ, Petrović P, Butić I, et al.

    BMC infectious diseases 2026; (26(1)).

    PMID: 42163150
  8. 8

    Case Report: Fulminant meningococcus-meningitis under treatment with ravulizumab despite complete vaccination-a rare but severe complication.

    Kozák G, Förster S, Haap M, et al.

    Frontiers in medicine 2026; (13()):1943514 doi:10.3389/fmed.2026.1943514.

    PMID: 42845921
  9. 9

    Atypical hemolytic uremic syndrome in kidney transplantation.

    Ponticelli C, Moroni G

    Journal of nephrology 2026; (39(7)):1334-1341 doi:10.1093/joneph/aajag096.

    PMID: 42742155
  10. 10

    Salvaging sepsis-associated atypical hemolytic uremic syndrome with terminal complement blockade: A case report.

    Qiu Y, Zhou S, Huang G, et al.

    Medicine 2026; (105(4)):e47281 doi:10.1097/MD.0000000000047281.

    PMID: 41578542
  11. 11

    A case report of atypical hemolytic uremic syndrome with a CFH mutation complicated by recurrent posterior reversible encephalopathy syndrome.

    Maruyama R, Takeuchi D, Momose M, et al.

    Medicine 2026; (105(27)):e49593 doi:10.1097/MD.0000000000049593.

    PMID: 42410819
  12. 12

    Ischemic cerebrovascular complications with initial presentation of genetic atypical hemolytic uremic syndrome.

    Sokola M, Toljan K, Almoushref A, et al.

    Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 2023; (32(8)):107238 doi:10.1016/j.jstrokecerebrovasdis.2023.107238.

    PMID: 37392483
  13. 13

    Early recognition of atypical hemolytic uremic syndrome to prevent irreversible kidney injury: cardiac failure and refractory hypertension as critical clues in young patients.

    Tsiamis N, Kole C, Stefanou E, et al.

    CEN case reports 2026; (15(2)).

    PMID: 41874770
  14. 14

    Atypical haemolytic uraemic syndrome: a case report of a rare cause of reversible cardiomyopathy.

    Campbell CM, Cassol C, Cataland SR, Kahwash R

    European heart journal. Case reports 2020; (4(2)):1-6 doi:10.1093/ehjcr/ytaa050.

    PMID: 32352052
  15. 15

    Ulcerative Colitis Gone Rogue: A Case of Complement-Mediated Thrombotic Microangiopathy in Inflammatory Bowel Disease.

    Yeboah EK, Thida AM, Moradi R, et al.

    Cureus 2025; (17(2)):e78447 doi:10.7759/cureus.78447.

    PMID: 40046371
  16. 16

    Seizure as the Presenting Symptom for Atypical Hemolytic Uremic Syndrome.

    Chan S, Weinstein AR

    The Journal of emergency medicine 2019; (56(4)):441-443 doi:10.1016/j.jemermed.2018.12.034.

    PMID: 30826084
  17. 17

    Atypical Hemolytic Uremic Syndrome in Children and Adults With the Hot Spot C3 Gene Variant p.Arg161Trp.

    Ter Steeg L, Bouwmeester RN, Ter Avest M, et al.

    Kidney international reports 2026; (11(8)):106599 doi:10.1016/j.ekir.2026.106599.

    PMID: 42318533
  18. 18

    Case Report: Possible C3 nephritic factor-driven complement-mediated severe hemolytic anemia and acute kidney injury in a child with Bordetella parapertussis infection.

    Thorsen SU, Hansen AT, Hartling HJ, et al.

    Frontiers in immunology 2025; (16()):1715464 doi:10.3389/fimmu.2025.1715464.

    PMID: 41550931
  19. 19

    From post-infectious glomerulonephritis to complement-mediated aHUS: a diagnostic challenge.

    Alzabali S, AlRasheed R, Alanazi A, et al.

    Pediatric nephrology (Berlin, Germany) 2026; (41(9)):2881-2883 doi:10.1007/s00467-026-07218-5.

    PMID: 41784797
  20. 20

    Postpartum Atypical Hemolytic Uremic Syndrome Complicating β-Thalassemia Intermedia: A Case Report and Literature Review.

    Gao B, Miao Y, Waseem S

    Journal of clinical medicine 2026; (15(14)) doi:10.3390/jcm15145740.

    PMID: 42513654
  21. 21

    Retinal disease in the C3 glomerulopathies and the risk of impaired vision.

    Savige J, Amos L, Ierino F, et al.

    Ophthalmic genetics 2016; (37(4)):369-376 doi:10.3109/13816810.2015.1101777.

    PMID: 26915021
  22. 22

    METAMORPHOPSIA AND ITS QUANTIFICATION.

    Simunovic MP

    Retina (Philadelphia, Pa.) 2015; (35(7)):1285-91 doi:10.1097/IAE.0000000000000581.

    PMID: 26049620
  23. 23

    Atypical hemolytic uremic syndrome: Consensus of diagnosis and treatment in Taiwan.

    Tseng MH, Lin SH, Tsai JD, et al.

    Journal of the Formosan Medical Association = Taiwan yi zhi 2023; (122(5)):366-375 doi:10.1016/j.jfma.2022.10.006.

    PMID: 36323601

This page is for informational purposes only and does not constitute medical advice. It explains warning signs associated with complement factor H deficiency and C5 inhibitor treatment; seek immediate care for emergency symptoms and follow your specialist’s instructions.

Guide contents complement factor H deficiency
Research & Literature
01 Understanding Complement Factor H (CFH) Deficiency 03 Biology and Subtypes